Well, I decided that while I was working on the leveling valve and air bag, I'd check everything in the area for leaks. I got my pump-up garden sprayer, filled it with soap and water, and sprayed all the hoses, valves, connections, whatever has to do with air. I saw a few bubbles on this part that's mounted on the differential. I have no clue what it is. I've not found it in my parts manual, either. I tried tightening the connection that was leaking, which didn't help. I cleaned it up some so I could see why it's leaking. There's a crack in it. I believe you can see the crack in the second pic. So, what is this part? It looks like a real pain to replace. Is it a pricey item? Thanks for any info.

When the control valve is operated, the Inversion valve operates permtting air in the isolated reservior to apply the brakes.

Its MCI part # 4B-29-1 from Mowhawk, they are about $75.00. you need one

David, before you remove it, take some masking tape or some other way to mark the hoses and make another of these great pictures to use for reference. The way its removed is that the hose comes off the top, then theres nut thats about 1- 1/14" that comes off and it drops off the bracket.

« Last Edit: July 19, 2006, 02:52:28 AM by ChuckMC8 »

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Far better is it to dare mighty things,to win glorious triumphs,even though they may be checkered by failure, than to rank with those poor spirits who neither enjoy nor suffer much,because they live in the gray twilight that knows neither victory nor defeat. Theodore Roosevelt (1858-1919)

Thanks for the info. What's the valve called that's mounted to the bulkhead in front of this valve (to the left in the first pic)? I didn't realize I had so much detail in that second pic... you can see the bubbles I thought I'd rinsed off! Thanks.

Thats the R-8 Relay valve. What happens is that when you press the brake pedal, air goes thru a small line back to said relay valve, where it makes the major air connection. (just like an electrical relay!)

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Far better is it to dare mighty things,to win glorious triumphs,even though they may be checkered by failure, than to rank with those poor spirits who neither enjoy nor suffer much,because they live in the gray twilight that knows neither victory nor defeat. Theodore Roosevelt (1858-1919)

Don't mean to be scary, but a friend of mine had a GM 4905 and he was parked in front of a church unloading sound equipment and the invesrion valve burst and it dumped evey bit of air and it ran away down a hill and was major. I know the rear brakes are supposed to be sping loaded and loss of air pressure lock them but in his case it was not good. Even so no road problem is good to deal with. Now you see that crack get with it. Good luck and Godspeed.

Thanks guys. I've taken longer than I thought to replace this leveling valve and air bag for a reason. Each time I work on something on this bus, I learn a lot. There's only so much that air line diagrams in the MCI manuals that one can learn. I've cleaned the grime, grease, and general dirt off almost all of the air components between the drive wheels. There's no better time than while the bus is sitting there in the yard, jacked up and blocked, with the tires/wheels off to find and correct any other problems. I always try to keep a good attitude about a repair that doesn't have to be completed on the road. There are two benefits to these sort of repairs. One, it didn't interrupt a trip, inconvenience me in any way, or cause any harm to anybody. Two, I most likely won't have to work on or replace that part again. If, for some reason, I do, it'll be much easier. I don't seem to have any other leaks in that area. After I finish here, I'll move to the airlines in the engine compartment and under the front. If it wasn't so damned hot and muggy and buggy here (the mosquitos here are horrible!), this would be closer to fun! Thanks again for the info and help.

Beatenbo,If your friend's Buff had inversion valves, it more than likely had DD3 rear cans on it and not spring brakes. Different beast altogether. And DD3s should hold the coach park brakes in case of air loss... gradual or immediate. DD3s use oblong ball bearing type rollers to hold the pushrod, and it would be strange indeed (if the park brakes were truly set) that both rear cans would be defective. I suspect that they were never set because of the inversion valve issue.

David,Good luck on your repairs. Even with the heat and humidity, you're right... it's better to fix these things on your own time and schedule and not be on the side of the road at oh-dark-thirty.

That sucker is gonna be a b*%# to get to. As big as these buses are, they sure made it difficult to get to some parts. Get it fixed...gotta go to Timmonsville soon!Once it ain't hot, it'll be too cold....That's my favorite excuse...too hot....too cold! As has already been stated...be certain to mark the hoses AND check the replacement valve for orientation...the R8 valve can be "clocked" so that various ports are oriented differently. Take lots of pix. The inversion valve isn't so bad...but the hoses can be mixed up. Use something that won't easily come off when working with the air lines. See ya, JR

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JR Lynch , Charlotte, NC87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.”

Spaceship, I don't know what he had, I just know he cleaned out a pine thicket. I had 3 Buffalos and never had an air issue except fo typical leaks. I had MC8,9, 96A3 now C-3 and never saw one like Dave's mounted on diff. I'm sure MCI is different, and Dave a ggod fan blowing under thre and best tool.

David: You have the right attitude on bus maintenance. Not only is it easier to fix things at home, but killing someone because of brake failure can really spoil your day. Don't even put your wheels back on until you are positive that the brake system is working properly. You are unlikely to drive the bus enough to ever wear out a part that you replace. Air leaks are a time consuming problem, but little technical knowledge is needed to repair them. It is rare to have loose fittings. Leaks usually require new hose or new device. Fortunately most air stuff is cheap. If you get the bus into a good state of repair, it will run trouble free for a llong time.